Peel the tape on that harness and look for a red wire, only solid red wire in that bundle, and see if the pin was pushed back out of the connector. If so, pry up the little tang on the pin so it will catch in the connector again. If no wire, you got me - maybe the 'lectron gremlins ate it...

Like you, I guess, I'm looking at the 91fsm. Should be the same as the 90, different from the 89, but the 89 manual has a much more complete description of how to disassemble the connectors.

Not responsible for advice not taken...